Method for making semiconductors for solar cells

Abstract

The invention relates to a method for producing a desired thin semiconductor film for use in solar cells. The desired semiconductor is grown epitaxially on a second semiconductor film which may be epitaxial on a third semiconductor. The second semiconductor has a lower melting point than the desired semiconductor. The temperature of the second semiconductor is increased. This creates a molten state in the second semiconductor and the desired semiconductor is stripped away from the second semiconductor. The desired film may be detached by dissolving the second semiconductor with a chemical agent that dissolves the second semiconductor.

We claim: 
     
       1. A method for producing a desired thin semiconductor film for use in solar cells comprising: a. growing epitaxially the desired semiconductor film on a second semiconductor film which has been epitaxially grown on a third semiconductor, the second semiconductor film having a lower melting point than the desired semiconductor film and the third semiconductor;   b. increasing the temperature of the second semiconductor film to create a molten state; and then   c. detaching the desired semiconductor film.   
     
     
       2. A method as recited in claim 1 wherein the desired semiconductor film, the second semiconductor film and the third semiconductor have a substantial lattice match. 
     
     
       3. A method as recited in claim 2 wherein the desired semiconductor film is substantially a single crystal. 
     
     
       4. A method as recited in claim 3 wherein the desired semiconductor is a film of silicon. 
     
     
       5. A method as recited in claim 3 wherein the second semiconductor is selected from the group consisting of Ge and Ge-Si alloy. 
     
     
       6. A method as recited in claim 3 wherein the second semiconductor is Ge-Si alloy. 
     
     
       7. A method as recited in claim 3 wherein the desired semiconductor film contains at least one pn junction. 
     
     
       8. A method as recited in claim 3 in which the third semiconductor is a single crystal. 
     
     
       9. A method as recited in claim 3 wherein the third semiconductor is a single crystal selected from the group consisting of Si and GaAs. 
     
     
       10. A method as recited in claim 3 wherein the third semiconductor is a single crystal selected from the group consisting of InAs and InP. 
     
     
       11. A method as recited in claim 3 wherein the third semiconductor is a single crystal selected from the group consisting of CdTe and CdSe. 
     
     
       12. A method as recited in claim 3 wherein the desired semiconductor film contains a plurality of different semiconductors. 
     
     
       13. A method as recited in claim 3 wherein the second semiconductor is selected from the group consisting of Ge and Ge-Si alloy and the third semiconductor being selected from the group of Si and GaAs. 
     
     
       14. A method as recited in claim 3 wherein the desired semiconductor film is a crystal selected from the group consisting of GaAs, GaAs x  P 1   -x , Al y  Ga 1   -y  As, AlSb and InP. 
     
     
       15. A method as recited in claim 3 wherein the desired semiconductor film is a crystal selected from the group consisting of CdTe and CdSe. 
     
     
       16. A method as recited in claim 3 wherein the desired semiconductor film is detached by a vacuum means. 
     
     
       17. A method as recited in claim 3 wherein the desired semiconductor film is detached by soldering metal contacts to the desired semiconductor, the solder having a melting point between the melting point of the second semiconductor, and the other two semiconductors (first and third). 
     
     
       18. A method as recited in claim 3 wherein the desired semiconductor film is detached by a slab that rides off the second semiconductor and carries the desired semiconductor film with it thereby detaching the desired semiconductor film from the second semiconductor. 
     
     
       19. A method as recited in claim 3 wherein the desired single crystal thin semiconductor film is formed of binary, ternary and quaternary semiconductors from columns II, III, IV, V and VI of the atomic periodic chart. 
     
     
       20. A method for producing a desired thin semiconductor film for use in solar cells comprising: a. growing epitaxially the desired semiconductor film on a second semiconductor film which has been epitaxially grown on a third semiconductor film, the second semiconductor having greater solubility in a chemical agent than the desired semiconductor film and the third semiconductor;   b. immersing the films in a chemical agent to dissolve the second semiconductor film; and then   c. detaching the desired semiconductor film.   
     
     
       21. A method as recited in claim 20 wherein the desired semiconductor film is selected from the group consisting of GaAs and InP. 
     
     
       22. A method as recited in claim 20 wherein the second semiconductor is selected from the group consisting of CdS and Al x  Ga 1   -x  As. 
     
     
       23. A method as recited in claim 20 wherein the third semiconductor is a single crystal selected from the group consisting of InP and GaAs. 
     
     
       24. A method as recited in claim 20 wherein the desired single crystal thin semiconductor film is formed of binary, ternary and quaternary semiconductors from columns II, III, IV, V and VI of the atomic periodic chart. 
     
     
       25. A method as recited in claim 20 wherein the desired semiconductor film is detached by a slab that rides off the second semiconductor during chemical dissolution and carries the desired semiconductor film with it thereby detaching the desired semiconductor film from the second semiconductor. 
     
     
       26. A method as recited in claim 20 wherein the desired semiconductor film is detached by a vacuum means during chemical dissolution of the second semiconductor.